Rehydrate in a mineral-rich sugar water solution (see "Water & minerals" below), changing the liquid every 24–48 hours, for up to 2–3 weeks before judging them non-viable. Very slow, faint bubbling is a normal early sign.

Switch to filtered, dechlorinated water and add a mineral source — a small piece of unrefined dried fruit, a pinch of unrefined salt, or a clean eggshell — each batch. Growth typically picks up within 2–4 cycles.

Move to plain refined cane sugar with a mineral addition (rather than coconut sugar or honey — see "Sugar & feeding"), and rest the grains for a few short 24-hour batches to recover before resuming your normal cycle.

If the grains still smell clean and are fermenting normally, this is cosmetic. Rinse in filtered water if you'd like to lighten them. See "Is it safe?" for how to tell this apart from true contamination.

Use filtered water, or leave tap water uncovered for 24 hours to let chlorine dissipate (this doesn't remove chloramine, which is more common in some areas — a carbon filter handles both). Spring or filtered water is the simplest reliable default.

Pick one mineral source per batch: a pinch of unrefined salt (not table salt), a clean crushed eggshell, a few mineral drops, or a piece of unsulphured dried fruit like a fig or raisin. You don't need all of them at once.

Plain refined cane sugar (white or raw) is the most reliable base — it ferments cleanly and predictably. If you want to experiment with an alternative, do it as an occasional batch rather than a permanent switch, and keep a backup batch on plain sugar.

Extend the first ferment by 12–24 hours and check again. If it's consistently flat even with more time, revisit grain health and mineral content first — a stressed colony ferments slowly regardless of timing.

A common starting ratio is around ¼ cup sugar per 1 litre of water, with roughly ¼ cup of grains. Make sure the sugar is fully dissolved in warm water before adding grains, and let the water cool to room temperature first.

Use taste rather than the clock as your main guide — ready is when it's mildly sweet-tart with a faint fizz. Expect roughly 24–48 hours at room temperature, shorter in summer, longer in winter.

Shorten the first ferment, move the jar somewhere cooler, or increase the sugar slightly to give the grains more to work with over the same time period.

Use swing-top bottles rated for pressure, keep second ferments to 24–48 hours rather than longer, and "burp" bottles once a day by briefly opening the seal over a sink. Refrigerate as soon as carbonation reaches where you want it — cold slows fermentation right down.

Check your bottle actually seals (swing-top gaskets wear out over time), add a small amount of extra sugar or fresh fruit juice, and confirm any juice used is 100% juice with no preservatives.

Use juice or strained purée instead of chunks, or strain the flavoured kefir through a fine mesh into a clean bottle before sealing for the second ferment.

Use plastic, silicone, or fine nylon mesh for straining and handling grains. Stainless steel is fine for a quick stir.

Use glass bottles specifically designed for carbonation (thick-walled swing-top or Grolsch-style bottles), never a repurposed thin glass bottle, and burp daily during the second ferment.

Label each jar with the start date and time, or stagger start times deliberately so you're only ever straining one batch a day.

Fuzzy or coloured raised spots: discard the batch and the grains, and start fresh in a clean jar. Brown strands or bottom sediment with no fuzz and a normal smell: strain as usual and continue — this isn't a safety concern.

For breaks longer than a month, dehydrate the grains for long-term storage. Check on fridge-rested grains every couple of weeks and refresh the sugar water if it looks depleted.

Split off the extra once the colony is noticeably larger than when you started. Spare grains can be eaten, blended into a smoothie, composted, dehydrated for later, or shared with someone starting out.

Increase the sugar-to-grain ratio slightly and move the jar somewhere cooler to stretch the ferment time out, or rest the grains in the fridge (see "Is it safe?") for planned breaks.

When scaling up significantly, increase the grain quantity roughly in proportion to the liquid, and check taste a little earlier than usual the first time until you've confirmed the new timing.